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install.packages("RMySQL")

library(RMySQL)

help(package="RMySQL") #查看说明文档

#创建数据库连接

con <- dbConnect(MySQL(), host="", dbname="", user="", password="")

 

summary(con) #获取连接信息

dbGetInfo(con) #获取连接信息

dbListTables(con) #查看database下所有表格

dbRemoveTable(con, "test") #删除名为test的表

#写数据库表

fruits <-data.frame(id=1:5,name=c("苹果","香蕉","梨子","玉米","西瓜"),price=c(8.8,4.98,7.8,6,2.1),status=c("无","打折","无","售罄","批发"))

dbListTables(con)

dbWriteTable(con,"fruits",fruits)

dbListTables(con)

#读数据库

dbReadTable(con,"fruits")#中文出现乱码，这是因为字符编码格式不统一的问题

dbSendQuery(con,'SET NAMES utf8')

 

#写数据表：直接/追加/覆盖

testA <-data.frame(id=1:6,e=c("a","b","c","d","e","f"),c=c("我","的","世","界","变","得")) testB <-data.frame(id=7:13,e=c("g","h","i","j","k","l","m"),c=c("奇","妙","跟","难","以","言","喻")) #直接写testA写入test表中 dbWriteTable(con,"test",testA,row.names=F) dbReadTable(con,"test") #追加写testB追加在test表后 dbWriteTable(con,"test",testB,append=T,row.names=F) dbReadTable(con,"test") #覆盖写testB覆盖test表 dbWriteTable(con,"test",testB,overwrite=T,row.names=F) dbReadTable(con,"test")

#用SQL语句查询结果

 

#直接获得查询结果 dbGetQuery(con, "SELECT * FROM fruits limit 3")

#给查询结果赋值 res <- dbSendQuery(con, "SELECT *FROM fruits")

#获取前2条数据，n=-1时是获取所有数据

data <- dbFetch(res, n=2) #再获取余下几条数据

data <- dbFetch(res, n=-1) #取余下所有数据

#清楚查询结果 dbClearResult(res) #断开连接 dbDisconnect(con)

#用SQL语句批量查询

con <- dbConnect(MySQL(),host="host",dbname="test_dw",user="user",password="password",client.flag= CLIENT_MULTI_STATEMENTS) #client.flag设置这样支持批量查询

dbSendQuery(con,'SET NAMES uft-8')

sql <- "SELECT * FROM fruits;SELECT * FROM test"

res1 <- dbSendQuery(con,sql) dbFetch(res1, n = -1)

if (dbMoreResults(con)) { res2 <- dbNextResult(con) dbFetch(res2, n = -1) }

dbListResults(con)

dbClearResult(res1)

dbClearResult(res2)